1. Technical Field
The present invention relates to an electronic field enhancement element, an analysis device, and an electronic apparatus.
2. Related Art
In various medical and health fields and in areas relating to environment, food, and public security, a sensing technology for rapidly and easily detecting trace substances with high sensitivity and high accuracy is required. The trace substances which are a target to be detected are very diverse and biologically-relevant substances such as bacteria, viruses, proteins, nucleic acids, and various antigens and antibodies or various compounds containing inorganic molecules, organic molecules, and polymers. In the related art, the detection of these trace substances was performed through sampling, analysis, and interpretation, but a dedicated device and a skillful inspection operator were necessary, and accordingly, it was difficult to perform the analysis without delay. Therefore, a long period of time (more than several days) is required to obtain results from an inspection. Thus, a sensing technology is strongly required to be rapid and simple, and development of a sensor which can respond to the requests is required. For example, a diagnosis of a patient in an airport showing signs of fever, along with diarrhea and emesis (vomiting) is an urgent issue, in order to prevent the spread of infectious diseases. In the infectious disease testing, different treatments are performed depending on the cause of the disease such as being bacterial or viral, and it is important to rapidly identify the type of bacteria or virus, in order to stop the spread of infection.
With such requests, in recent years, various types of sensors using an electrochemical method have been investigated, and an interest in a sensor using surface plasmon resonance (SPR) has increased due to integration ability, low cost, and a high degree of freedom of the measurement environment. For example, a sensor which detects adsorption of the substance such as adsorption of antigens in an antigen-antibody reaction using the SPR generated on a metal thin film provided on a surface of a total reflective prism, has been known. A method of detecting Raman scattering of the substance attached to a sensor portion using surface enhanced Raman scattering (SERS) and identifying the attached substance has also been investigated.
As a structure of such as sensor, OPTICS LETTERS, Vol. 30, No. 24, 2005, 3404-3406, for example, discloses a sensor element having a structure (Gap type Surface Plasmon Polariton (GSPP) structure) in which a SiO2 thin film is formed on a gold thin film and a gold disk is formed thereon.
The element disclosed in OPTICS LETTERS, Vol. 30, No. 24, 2005, 3404-3406 employs a SiO2 layer as a dielectric body disposed between a metal layer and a metal particle. However, according to the investigation of the inventors, it has been found that a refractive index of a dielectric layer strongly affects a degree of electronic field enhancement of the element and distribution of a hot spot.